863 research outputs found
Membrane solitons in eight-dimensional hyper-Kaehler backgrounds
We derive the BPS equations satisfied by lump solitons in -dimensional
sigma models with toric 8-dimensional hyper-K\"ahler () target spaces
and check they preserve 1/2 of the supersymmetry. We show how these solitons
are realised in M theory as M2-branes wrapping holomorphic 2-cycles in the
\bE^{1,2}\times {HK}_8 background. Using the -symmetry of a probe
M2-brane in this background we determine the supersymmetry they preserve, and
note that there is a discrepancy in the fraction of supersymmetry preserved by
these solitons as viewed from the low energy effective sigma model description
of the M2-brane dynamics or the full M theory. Toric manifolds are
dual to a Hanany-Witten setup of D3-branes suspended between 5-branes. In this
picture the lumps correspond to vortices of the three dimensional or theory.Comment: 12+1 pages. LaTex. v2: Typos corrected and references adde
STRINGY EVIDENCE FOR D=11 STRUCTURE IN STRONGLY COUPLED TYPE II-A SUPERSTRING
Witten proposed that the low energy physics of strongly coupled D=10 type-IIA
superstring may be described by D=11 supergravity. To explore the stringy
aspects of the underlying theory we examine the stringy massive states. We
propose a systematic formula for identifying non-perturbative states in D=10
type-IIA superstring theory, such that, together with the elementary excited
string states, they form D=11 supersymmetric multiplets multiplets in SO(10)
representations. This provides hints for the construction of a weakly coupled
D=11 theory that is dual to the strongly coupled D=10 type IIA superstring.Comment: LaTeX, revtex, 2-column, 10 pages
Dyonic p-branes from self-dual (p+1)-branes
The `electromagnetic' Sl(2;\bZ) duality group in spacetime dimension
can be given a Kaluza-Klein interpretation in as the modular group of
a compactifying torus. We show how dyonic -branes in can be
interpreted as self-dual -branes in wound around the homology
cycles of the torus. In particular, dyons of the D=4 N=4 heterotic string
theory are interpreted as winding modes of a D=6 self-dual string, while D=8
dyonic membranes are interpreted as wound 3-branes of D=10 IIB superstring
theory. We also discuss the T-dual IIA interpretations of D=8 dyonic membranes.Comment: 16 pp. phyzzx. 1 fi
Compactification of D=11 supergravity on spaces of exceptional holonomy
We investigate the compactification of D=11 supergravity to D=5,4,3, on
compact manifolds of holonomy (Calabi-Yau), , and ,
respectively, making use of examples of the latter two cases found recently by
Joyce. In each case the lower dimensional theory is a Maxwell/Einstein
supergravity theory. We find evidence for an equivalence, in certain cases,
with heterotic string compactifications from D=10 to D=5,4,3, on compact
manifolds of holonomy (), , and ,
respectively. Calabi-Yau manifolds with Hodge numbers play
a significant role in the proposed equivalences.Comment: Minor amendments plus some new reference
Analysis of travelling waves associated with the modelling of aerosolised skin grafts
A previous model developed by the authors investigates the growth patterns of keratinocyte cell colonies after they have been applied to a burn site using a spray technique. In this paper, we investigate a simplified one-dimensional version of the model. This model yields travelling wave solutions and we analyse the behaviour of the travelling waves. Approximations for the rate of healing and maximum values for both the active healing and the healed cell densities are obtained
Intersecting M-branes
We present the magnetic duals of G\"uven's electric-type solutions of D=11
supergravity preserving or of the D=11 supersymmetry. We interpret
the electric solutions as orthogonal intersecting membranes and the
magnetic solutions as orthogonal intersecting 5-branes, with ; these
cases obey the general rule that -branes can self-intersect on
-branes. On reduction to these solutions become electric or
magnetic dilaton black holes with dilaton coupling constant (for )
or (for ). We also discuss the reduction to D=10.Comment: Derivation of an intersection rule added. Some additional refs.
Version accepted for publication in PLB. Phyzzx macr
Phase field analysis of eutectic breakdown.
In this paper an isotropic multi-phase-field model is extended to include the effects of anisotropy and the spontaneous nucleation of an absent phase. This model is derived and compared against a published single phase model. Results from this model are compared against results from other multi-phase models, additionally this model is used to examine the break down of a regular two dimensional eutectic into a single phase dendritic front
Duality of Type II 7-branes and 8-branes
We present a version of ten-dimensional IIA supergravity containing a 9-form
potential for which the field equations are equivalent to those of the
standard, massless, IIA theory for vanishing 10-form field strength, ,
and to those of the `massive' IIA theory for non-vanishing . We present
a multi 8-brane solution of these equations that generalizes the 8-brane of
Polchinski and Witten. We show that this solution is T-dual to a new multi
7-brane solution of compactified IIB supergravity, and that the latter is
T-dual to the IIA 6-brane. When combined with the U-duality of the
type IIB superstring, the T-duality between type II 7-branes and 8-branes
implies a quantization of the cosmological constant of type IIA superstring
theory. These results are made possible by the construction of a new {\it
massive} N=2 D=9 supergravity theory. We also discuss the 11-dimensional
interpretation of these type II p-branes.Comment: Includes corrections to last section that will appear in the version
to be published in Nuclear Physics B. 36 pp. Phyzz
Massive IIA supergravity from the topologically massive D-2-brane
The superfield equations of massive IIA supergravity, in the form of
constraints on the superspace geometry, are shown to be implied by
-symmetry of the topologically massive D-2-brane.Comment: 19 pp. Minor corrections. To appear in PL
Mersenne Primes, Polygonal Anomalies and String Theory Classification
It is pointed out that the Mersenne primes and associated
perfect numbers play a significant role in string
theory; this observation may suggest a classification of consistent string
theories.Comment: 10 pages LaTe
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